1. Field of the Invention
This invention relates to a hardware control circuit and, more particularly, to a device and method for detecting a type of a fan.
2. Description of the Related Art
According to a heat dissipating design of an electronic product, a fan is mostly used to guide airflow and to dissipate heat. Usually, there are two types of a small fan. The first type is a three-pin fan which changes a rotating speed thereof via a direct-current (DC) voltage; the other type is a four-pin fan which includes one with built-in rising resistors and one without rising resistors. The four-pin fan controls a rotating speed thereof via a pulse width modulation (PWM) signal.
According to the prior art of detecting a type of a fan, for example, in a U.S. application publication No. 20090169188 titled “APPARATUS AND METHOD FOR FAN AUTO-DETECTION”, software and hardware are used to detect a type of a fan and to control a rotating speed of the fan. In detail, a voltage of the fan is determined to generate a control signal and thus the control signal is transmitted to a PWM generator and a DC adjustor. Further, a rotating speed of the fan is detected. That is, whether the rotating speed of the fan changes with the signal of the PWM generator is detected. In a Chinese patent No. 2864764 titled “DEVICE FOR CONTROLLING DRIVING FAN”, an identification code of a fan is used to detect a type of the fan. In detail, a fan type identification module transmits protocol data, and after the fan receives the protocol data, the fan transmits an identification code to a driving signal setting module to inform the driving signal setting module of the type of the fan. During determination of the type of the fan, since the fan type identification module needs to transmit the protocol data to the fan, a controller capable of transmitting the protocol data needs to be built in the fan, thereby expending extra cost. In a U.S. Pat. No. 7,313,466 titled “SYSTEM AND METHOD FOR AUTOMATICALLY DETECTING A TYPE OF A CPU FAN”, software is used to detect a type of a fan. In detail, a PWM signal is controlled by the software, and a change of a rotating speed of the fan is determined by adjusting the PWM signal. However, only a rotating speed of a four-pin fan changes according to a PWM signal.